Logging/downhole measurements strategy

The best target depths for installation of the observatory components can be identified via LWD, which is performed to monitor drilling conditions and to define lithological and structural changes in real time. The LWD tools selected for Expedition 343 include the TeleScope 675 MWD, located above the geoVISION 675 (Fig. F7), which not only measures drilling parameters and transmits these data in real time but also stores data on the tool memory recorder for later downloading once recovered on deck. A gap of several meters from the top of the bit and the sensor pads causes a time delay between the bit drilling and the sensors collecting data and transferring them to memory. The geoVISION has five resistivity measurements, three-azimuth electrical imaging, and gamma ray measurement. The resistivity tool is based on resistivity-at-the-bit technology to provide real-time at-bit resistivity data and azimuthally focused laterolog measurements for detailed geological imaging on the borehole wall. The geoVISION tool also contains a scintillation counter that provides a total gamma ray measurement. Current plans also include the provision tool, which uses magnetic resonance techniques to independently constrain the quantities of the fluids in the sediment, the properties of the fluids, and the sizes of the pores that contain the fluids. However, actual tools used during the expedition may change according to availability.

TeleScope MWD tools include the capability to transmit annular pressure while drilling (APWD) and MWD data and provide information to optimize well placement, improve drilling efficiency, and reduce risk. APWD measurements also include weight on bit and torque on bit data, which are valuable data sets for drilling safety and efficiency.